Domestic spraying device

ABSTRACT

A hand-held domestic spraying product comprising a reservoir ( 2 ) holding a liquid composition ( 3 ), a nozzle means ( 17 ) for producing a spray from said liquid composition, an electrically powered pump ( 4 ) for creating the force required to move the liquid composition from the reservoir towards the nozzle, and a control means for activating the electrically powered pump ( 4 ), characterised in that the electrically powered pump ( 4 ) is a MEMS pump.

The present invention relates to a hand-held domestic spraying deviceand product that utilises a MEMS (micro-electro mechanical system) pumpto force a liquid composition from a reservoir towards a spray nozzle.

Hand-held domestic spraying devices of the prior art have utilised avariety of means for transferring a liquid composition from a storagereservoir towards a spray nozzle. A widely used option has been to usevolatile propellants, such as liquefied hydrocarbons orchlorofluorocarbons, to pressurise the liquid composition. However, itis increasingly recognised that the addition to the atmosphere ofVOCs/greenhouse gases may have detrimental environmental consequences.

An alternative means of supplying the necessary force to the liquidcomposition has been the use of hand-powered mechanical mechanisms, suchas squeeze spray and trigger spray devices. Unfortunately, suchmechanisms suffer the inherent problem of requiring physical effort onthe part of the consumer. In addition, devices utilising such mechanismstend not to produce good quality sprays.

The problems of the above approaches have been overcome by the use ofelectrically powered pumps. Such pumps may be used directly on theliquid composition or they may be used as air pumps—the resulting airpressure modification providing the force required to move the liquidcomposition. EP 949,006 A1 (Procter and Gamble) describes the use of anelectrically powered pump to directly move a liquid cleaning compositionfrom a reservoir towards a spray nozzle. U.S. Pat. No. 3,522,911(Collins) and U.S. Pat. No. 4,034,916 (Helene Curtis) describe the useof electrically powered air pumps as compressors, supplying pressurisedair that is used to force a liquid composition from a reservoir towardsa nozzle. WO 99/49904 (Quest International) describes the use of anelectrically powered air pump to create an air stream that draws aliquid composition from a reservoir using a venturi effect.

The problem with electrically powered pumps, as described above, is thatthey are generally relatively expensive and bulky. In addition, theirpower consumption can be quite high. As a result, traditionalelectrically powered pumps are not ideal for use in disposable,hand-held, domestic spray products. For this reason, devices thatutilise such pumps have previously been envisaged as non-disposableproducts, requiring re-fill packs of the liquid composition to bedispensed in order to be economically viable.

We now have found that a hand-held domestic spray product utilising anelectrically powered pump may be made using a MEMS pump. Such productshave all the benefits of electrically powered pumps described above andthe further benefits of being relatively inexpensive and light. Inaddition, the relatively low cost and size of such products makes thempotentially disposable and not tied to use with re-fill packs. A furtheradvantage is that such products can produce a spray with very littlenoise; this can be a valuable benefit in the domestic environment.

MEMS pumps have previous been described for use in military andlaboratory applications. WO 00/28215, U.S. Pat. No. 5,836,750, U.S. Pat.No. 6,106,245, and U.S. Pat. No. 5,836,750 (all by Honeywell Inc.)describe such pumps and usage.

SUMMARY OF THE INVENTION

In a first aspect of the present invention, there is provided ahand-held domestic spraying product comprising a reservoir holding aliquid composition, a nozzle means for producing a spray from saidliquid composition, an electrically powered pump for creating the forcerequired to move the liquid composition from the reservoir towards thenozzle, and a control means for activating the electrically poweredpump, characterised in that the electrically powered pump is a MEMSpump.

In a second aspect of the present invention, there is provided a methodof spraying a liquid composition using a product as described in thefirst aspect of the invention.

DETAILED DESCRIPTION

The hand-held spraying product of the present invention may be used withnumerous liquid compositions and for many domestic applications. It isparticularly suitable for application of cosmetic compositions, whichare generally applied directly to the human body. Examples of suchcosmetic compositions include hair sprays, perfume sprays, deodorantbody sprays and underarm products, in particular antiperspirantcompositions. The MEMS pump provides a means of moving the liquidcomposition from the reservoir towards the nozzle and a good sprayquality to be produced. A further benefit resulting from the use of anelectrically powered MEMS pump is that the spray product iscomparatively energy efficient, the MEMS pump having a relatively lowpower consumption. The above benefits are independently and collectivelyadvantageous for liquid cosmetic compositions that have to be applied tothe human body, where it is desirably to be able to apply thecomposition quickly in the form of a good quality spray and also to havea product that does not quickly run out of power.

Any type of MEMS pump may be used in the spray product of the invention.The pumps are characterised by comprising micro-channels havingsub-millimeter diameters and operating using electrostatic pressuregeneration. Typical micro-channel diameters are from 1 to 500 μm, inparticular from 10 to 300 μm. The pumps are typically fabricated usingprocesses compatible with those used in semi-conductor integratedcircuit production. Typical materials of manufacture are silicones andplastics, with the proviso that the material must be capable of beingelectrically charged. The pumps may operate by positive displacement,the different principles being piston, gear, lobe, mohno, diaphragm,centrifugal, and hose. Micro-peristaltic pumps are another option. Theuse of diaphragm pumps, where liquid displacement is achieved by thedeformation of an elastic membrane, is a preferred option. Diaphragmpumps that are electrostatically driven are particularly preferred,especially those having a plurality of elementary cells, each of saidcells comprising a body forming an electrode cavity having at least oneelectrode having a curved surface facing toward a curved surface on afacing part of said body to define said cavity, said body includingelectrical activation means for selectively energising said electrode; adiaphragm mounted and grounded in said body under tension and having amajor portion located in said cavity between said curved surfaces, saiddiaphragm being adapted to deflect toward and away from said electrodecurved surface; lateral conduit means in said body forming an endconduit, said lateral conduit means being operably connected to theportion of said diaphragm mounted in said body and positioned to beopened and closed by movement of said diaphragm for controlling flow offluid through said end conduit; vertical conduit means operativelyconnected to at least one curved surface of said cavity for controllingflow of fluid there through by movement of said diaphragm into and outof contact with said vertical conduit means; and interconnecting conduitmeans for connecting said cell to said plurality of cells to form saidMEMS pump; whereby activation of said electrode causes movement of saiddiaphragm toward said curved surface of said electrode and deactivationof said electrode allows said diaphragm to return to its originalposition, to thereby move fluid into and out of said body.

In order to achieve a good transfer rate for the liquid composition, anarray of MEMS pumps arranged in parallel may be used, optionally withoutput micro-channels combining together to give a single chamber. Anarray of MEMS pumps arranged in series may be used in order to achievehigher pressures. Preferably, the MEMS pumps may be arranged both inparallel and in series in order to achieve both of the above benefits.

The MEMS pump may be used to act directly upon the liquid composition,forcing it towards the nozzle means. In such embodiments, the MEMS pumpacts as a liquid pump and is situated either within or adjacent to thereservoir holding the liquid composition or is connected thereto by aconduit which provides for transfer of the liquid composition from thereservoir to the MEMS pump.

In preferred embodiments, the MEMS pump acts as an air pump and resultsin an air pressure modification adjacent to the liquid composition andthereby provides the force required to move the liquid compositiontowards the nozzle means. Such embodiments have the benefit that theliquid composition is not in direct contact with the MEMS pump, therebyavoiding any incompatibility problems. This is of particular benefitwhen the liquid composition has a resistivity of less than 10⁴ ohm.cm,especially when the MEMS pump is a diaphragm pump that iselectrostatically driven.

In certain embodiments in which the MEMS pump acts as an air pump, itsfunction is to act as an air compressor, increasing the air pressureadjacent to the liquid composition. The pressure upon the liquidcomposition then forces it towards the nozzle means, often via atransfer conduit.

In other embodiments in which the MEMS pump acts as an air pump, it actsto create an air stream that serves to draw the liquid composition fromthe reservoir using a venturi effect. In such embodiments, the air flowsthrough a channel and creates a reduced pressure environment adjacent tothe liquid composition, typically at the outer end of a transfer conduitcontiguous with the reservoir for the liquid composition. The reducedpressure draws the liquid composition from the reservoir and into theair stream. The cross-sectional area of the transfer conduit for theliquid composition is preferably greater than that of the air flowchannel at the point where the two meet—this can lead to enhanced thespray quality. The outer end of the transfer conduit may be consideredto be part of the nozzle means (vide infra) in some embodiments.

A problem that may occur with products according to the presentinvention is that the MEMS pump may produce a pulsing flow, which can bedetrimental to spray quality. It is therefore desirable to have a pulsereduction means present. Such means may comprise a parallel array ofMEMS pumps, generally a parallel array of MEMS pumps in series, withnon-synchronous pulse frequencies, by which it is meant that thefrequencies are different or that they are out of phase with oneanother, preferably producing an even total flow on combined use. Inembodiments in which the MEMS pump acts as an air pump, in particular asan air compressor, an alternative or additional pulse reduction meansmay comprise a buffer chamber for receiving the air from the MEMS pumpor pumps. When present, it is preferred that the buffer chamber has avolume of at least half that of the reservoir containing the liquidcomposition in order to enhance its effectiveness.

The nozzle means is responsible for creating and often directing thespray produced from the liquid composition. The nozzle means may be anyof those typically used in the art, ranging from simple exit orifices tomore complicated venturi atomisation nozzles. Preferred nozzles comprisea means of increasing droplet break-up beyond that achieved by thepassage of the liquid composition through a simple exit orifice. Swirlchambers of the type known in the art are suitable for use in thismanner.

The control means for activating the electrically powered pump may be ofany appropriate form. Typical examples include push buttons, toggleswitches, or slide-operated switches. The activation will typicallyinvolve supply of electrical power to the pump.

The source of the electrical power is preferably comprised within thedevice itself, although an external power supply may be used. Theproduct may comprise a capacitor, battery or photo-voltaic cell as asource of electrical power.

In many embodiments there exists a transfer conduit for transfer of theliquid composition from the reservoir towards the nozzle means. Thetransfer conduit may have various positions relative to the MEMS pump.When the MEMS pump acts directly upon the liquid composition, thetransfer conduit may be located between the reservoir and the pump,between the pump and the nozzle means, or there may be a transferconduit in both of these locations. When the MEMS pump acts an aircompressor, the transfer conduit runs from the reservoir to the nozzlemeans, the MEMS pump being separately located.

When present, the transfer conduit preferably comprises one or morevalves. Such valves may function to prevent leakage of the liquidcomposition from the reservoir when the pump is not operating. Positivepressure on the reservoir side of the valve or negative pressure on thenozzle side of the valve may cause the opening of such valves.

For hand-held spraying products in which the MEMS pump acts as an airpump, it is preferred that the air pump is able to operate at high airflow rate, for example from 30 L/hr. to 150 L/hr., and, in particular,from 42 L/hr. to 120 L/hr. For such products, the pressure generated bythe air pump is preferably from 15 to 40 psig. Such flow rates and/orpressures enhance the spray quality achieved. Spray quality may bedefined by the fineness of the droplets achieved and/or by thenarrowness of the particle size distribution (p.s.d.) of said droplets.For many applications, it is desirable to achieve a volume mean dropletsize of from 1 μm to 100 μm, in particular from 5 μm to 50 μm, andespecially from 5 μm to 25 μm. It is desirable that the narrowness ofthe p.s.d. is such that the D[10] to D[90] spread is from 1 μm orgreater to 100 μm or less, in particular from 5 μm or greater to 85 μmor less and especially from 5 μm or greater to 35 μm or less. Thedroplet/particle size values quoted are as measured by conventionallight scattering techniques on instruments such as the MalvernMastersizer.

Liquid compositions used with the product of the present inventionfrequently comprise a liquid carrier fluid comprising a C2 to C4alcohol, for example ethanol, propylene glycol, propanol, oriso-propanol. When such liquid compositions are cosmetic compositionsfor application to the human body, the good spray quality attained leadsto an excellent sensory benefit for the user. Suitable liquidcompositions typically comprise C2 to C4 alcohol at a level of from 5%to 95%, in particular from 25% to 80%, and especially from 40% to 75% byweight of the composition. Liquid compositions comprising ethanol areparticularly suitable for use with the product of the present invention.In certain embodiments, as described above, it is preferred that theliquid composition has a conductivity of less 10⁴ ohm.cm. Suchcompositions typically comprise water, for example at a level of from 5to 95%, in particular from 10 to 80%, and especially at from 20 to 60%by weight of the total composition. Such compositions may also comprisea solubilised aluminium salt, for example at from 0.5 to 20%, inparticular from 1 to 15%, and especially at from 2 to 10% by weight ofthe total composition.

The invention will now be further described by reference to two specificembodiments as represented by FIGS. 1 and 2.

FIG. 1 is a representation of an embodiment in which the MEMS pump actsas an air compressor.

FIG. 2 is a representation of an embodiment in which the MEMS pump actsto create an air stream that serves to draw the liquid composition fromthe reservoir using a venturi effect.

In FIG. 1, the spray product represented comprises a body (1) withinwhich there is a reservoir (2) for a liquid composition (3), and anarray of MEMS pumps (4) arranged in vertical series (20 per series), theseries being arranged in parallel (in a 3×3 array). The MEMS pumps (4)are powered by a battery (5) and are activated by pressing a button (6),via an electronic control unit (7) and associated circuitry (8). TheMEMS pumps (4) draw air from outside of the device through an inletvalve (9) which opens when the pressure in an entry chamber (10) isreduced by the operation of the MEMS pumps (4). The air is pumped by theMEMS pumps (4) into a buffer chamber (11), through tubes (12) runningfrom the top of each series of MEMS pumps (4). The air in the bufferchamber (11) may be allowed to build in pressure, until it is releasedto flow through a channel (13) by the opening of a valve (14), which isalso controlled by the electronic control unit (7) via the associatedcircuitry (8).

The air flows through the channel (13) into the reservoir (2) holdingthe liquid composition (3). When a further valve (15), which is alsocontrolled by the electronic control unit (7) via the associatedcircuitry (8), is released, the liquid composition (3) is forced up atransfer conduit (16) towards the nozzle (17) where it is atomised andexits as a spray. A vapour phase tap (not shown) is optionally presentas part of the nozzle design.

In FIG. 2, many of the features serve the same function as in FIG. 1 andthe descriptions given for the features of FIG. 1, apply equally to thefeatures labelled the same in FIG. 2. Differences exist when the airleaves the buffer chamber (11) via air flow channel (13). In theembodiment of FIG. 2, the channel (13) leads directly towards the nozzle(17) via a narrower section of the channel (18). Shortly before thischannel (18) reaches the nozzle (17), it passes over the top of atransfer conduit (16) which is of greater cross-sectional area than thatof the narrower section of the air flow channel (18) at the point wherethe two meet. When a valve (15) is opened, the air flow draws the liquidcomposition (3) up the transfer conduit (16) by a venturi effect.Atomisation of the liquid composition (3) commences at the point (19)where it is hit by the air stream and is further enhanced by the nozzle(17) with the result that a spray issues from said nozzle (17). Negativepressure is not allowed to build on loss of the liquid composition (3)from the reservoir (2)—air is allowed to enter the upper section thereservoir through an air bleed (20) and a ‘vacuum break’ valve (21)which opens when the pressure in the reservoir (2) is reduced.

1. A hand-held domestic spraying product comprising a reservoir holdinga liquid composition, a nozzle means for producing a spray from saidliquid composition, an electrically powered pump for creating the forcerequired to move the liquid composition from the reservoir towards thenozzle, and a control means for activating the electrically poweredpump, characterised in that the electrically powered pump is a MEMSpump.
 2. A product according to claim 1, wherein the MEMS pump acts asan air pump resulting in an air pressure modification adjacent to theliquid composition and providing the force required to move the liquidcomposition from the reservoir towards the nozzle means
 3. A productaccording to claim 2, wherein the liquid composition has a resistivityof less than 10⁴ ohm.cm.
 4. A product according to claim 3, wherein theMEMS pump is a diaphragm pump that is electrostatically driven.
 5. Aproduct according to claim 2, wherein the MEMS pump acts as aircompressor, increasing the air pressure adjacent to the liquidcomposition.
 6. A product according to claim 2, wherein the MEMS pumpacts to create an air stream that serves to draw the liquid compositionfrom the reservoir using a venturi effect.
 7. A product according toclaim 1, comprising a pulse reduction means.
 8. A product according toclaim 1, comprising a parallel array of MEMS pumps.
 9. A productaccording to claim 1, comprising an array of MEMS pumps in series.
 10. Aproduct according to claim 8, comprising a parallel array of MEMS pumpswith non-synchronous pulse frequencies.
 11. A product according to claim2, comprising a buffer chamber for receiving the air from the MEMS pump.12. A product according to claim 11, wherein the buffer chamber has avolume of at least half that of the reservoir containing the liquidcomposition.
 13. A product according to claim 1, comprising a transferconduit for transfer of the liquid composition from the reservoirtowards the nozzle means.
 14. A product according to claim 13, whereinthe transfer conduit comprises one or more valves.